Measurement of Nitrous Acid in Blodgett Forest during BEARPEX 2007
Abstract
Nitrous acid (HONO) is an important precursor of hydroxyl radical (OH) in the atmosphere. Understanding HONO chemistry especially its contribution to HOx (= OH + HO2) budget and its heterogeneous formation is very important to understand atmospheric oxidation processes. A highly sensitive instrument based on LOng Path Absorption Photometry (LOPAP) for detecting atmospheric HONO was deployed in Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) in summer 2007 in Blodgett Forest, California. The median diurnal variation shows a minimum HONO level of about 30 pptv in the morning and a maximum level of 60-70 pptv in the evening, which is different from the observations at some other forested sites. Measured HONO correlates well with measured NO2, indicating that heterogeneous processes involving NO2 might be the main HONO source in this environment. Vertical gradients of HONO were measured from the ground surface to 18 meters above ground level. Relatively large HONO gradients within the canopy and less HONO gradients above the canopy were observed. The LOPAP HONO measurements were compared with the HONO measurements by a Chemical Ionization Mass Spectrometer (CIMS) on three days. Good agreement was obtained between the two completely different techniques. Using the extensive measurement suite of chemical species and meteorological parameters, the contribution of HONO photolysis to HOx budget is calculated and heterogeneous formation of HONO under different conditions is discussed.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.A32C..01R
- Keywords:
-
- 0345 Pollution: urban and regional (0305;
- 0478;
- 4251);
- 0365 Troposphere: composition and chemistry;
- 0478 Pollution: urban;
- regional and global (0345;
- 4251);
- 4852 Photochemistry